For Your Child

Better Vision in Children Linked to the Outdoors

Kids who spend more time outside - and away from the television set - are less likely to develop myopia, the inability to see things clearly at a distance.

The findings were published in the medical journal Optometry and Vision Science.

The new report does not determine whether too much indoor activity actually causes poor eyesight. And at this point, researchers have not pinpointed what the exact mechanism might be.

Still, "it would seem prudent to encourage outdoor activities - not necessarily sports - for all growing children and young adults in order to reduce the progression of myopia," says Howard C. Howland, Ph.D., at Cornell University.

About a third of Americans suffer from myopia, says study author Jane Gwiazda,Ph.D., director of research at The New England College of Optometry.

The condition seems to be caused by both genetics and the environment, Dr. Gwiazda says. The condition is more common in people who engage in a lot of "near work" due to their jobs, she notes.

Light and Distance Affects Development

The study authors gave questionnaires to the parents of 191 children who were at an average age of 13 years. Among other things, the researchers asked about the children's time spent using the computer, reading for pleasure, and watching TV.

During the study, the children's eyesight was tested annually.

The children who developed myopia - also known as nearsightedness - spent less time in outdoor activities, an average of 8 hours a week compared to nearly 13 hours among the other children.

Those with myopia also watched more television (12 hours vs. eight hours a week).

What is going on?

"One possibility is that all the hours spent viewing objects at a distance rather than up close, as happens outdoors, provides a 'stop' signal to block myopia progression," explains Dr. Gwiazda.

"Outdoor exposure also may be beneficial, because sunlight causes the pupil to constrict, resulting in a larger depth of focus - the range in which objects appear clear - and less image blur that's associated with myopia development," she says.

In other words, the eye may see more clearly outside in the sunlight and lessen the likelihood for developing myopia.

Varying Activities a Plus

Looking at things farther away may be another benefit of outdoor activities.

"We know a great deal about what causes myopia in animals, including primates," says Dr. Howland. "Images that are focused behind the retina cause the eye to grow in length, making the animal more myopic.

Generally speaking, one can prevent animals from becoming myopic if they are provided with sufficient opportunity to see distant objects," he says.

In popular culture, bookworms and nerds are often depicted as wearing glasses. Some studies have indeed shown a connection between heavy reading and myopia, Dr. Gwiazda says. But the new research does not confirm that link.

"In our study, children with more hours of outdoor activity do not necessarily spend less time reading and using computers," says Dr. Gwiazda.